IC wherein a chopper-type buck regulator PNP switch supplies base current to the load

ABSTRACT

A chopper-type regulator circuit includes an output transistor composed of a PNP-type transistor, and a control section for controlling switching of the output transistor based upon a voltage difference between a reference voltage and an output voltage. The control section is provided with a base current output terminal for supplying a base current of the output transistor to a load connected to the chopper-type regulator circuit.

This application is a continuation of application Ser. No. 08/563,766now U.S. Pat. No. 5,670,866, filed on Nov. 28, 1995, the entire contentsof which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a chopper-type regulator circuit and achopper-type regulator IC that stabilize an output voltage bycontrolling switching of an output transistor which is a PNP-typetransistor based upon a voltage difference between a reference voltageand the output voltage.

BACKGROUND OF THE INVENTION

In order to obtain a stabilized d.c. voltage which is required forelectronic equipment, etc., a regulator circuit is generally used. Thereis a step-down-typos regulator circuit which obtains an output voltagelower than an input voltage as one kind of such a regulator circuit. Thestep-down-type regulator has two types.

The first one is a regulator circuit which is called a dropper system,and the dropper system has the advantages of low noises and of simpledesign. This is used in a place where a difference (voltage difference)between an input voltage and an output voltage is small.

The second one is a regulator circuit that is called a chopper system,and the chopper system has the advantages of good efficiency in the casewhere the difference between the input voltage and the output voltage islarge.

The following will concretely discuss the regulator circuit having thechopper system.

FIG. 8 is a block diagram which shows an electrical configuration of thechopper-type regulator circuit (hereinafter, referred to as theregulator circuit) which controls a pulse width of a voltage mode. Aregulator circuit 13 is composed of a reference voltage circuit 1, anerror amplifier 2, an oscillator 3, a PWM (Pulse Width Modulation)comparator 4, a drive transistor 5 which is a PNP-type transistor and anoutput transistor 6 which is an NPN-type transistor. The regulatorcircuit 13 stabilizes the output voltage by controlling the pulse widthof the voltage mode.

Here, a catch diode 7, a coil 8, a voltage dividing circuit composed oftwo resistors 9 and 10, and an output capacitor 11 as indispensableconstituents are mounted to the outside of the regulator circuit 13, andbut for them, the output voltage cannot be obtained (in the drawing, 12represents a load).

Next, an operation of the regulator circuit 13 will be explained. FIGS.9(a) through 9(f) are drawings which shows waveforms of main signals.

First, when an input voltage V_(IN) shown in FIG. 9(a) is applied to aninput terminal IN, the regulator circuit 13 is actuated. Then, an outputvoltage V₀ is divided by the voltage dividing circuit composed of theresistors 9 and 10 connected to a load 12, and the divided voltage isfed back into a feedback terminal ADJ. Since the feedback terminal ADJis connected to a reverse input of the error amplifier 2, the erroramplifier 2 outputs an error signal (differential voltage) obtained byamplifying a voltage difference between the divided voltage and areference voltage outputted from the reference voltage circuit 1. Theerror signal is represented by a voltage waveform W1 of FIG. 9(b).

Meanwhile, in the PWM comparator 4, a voltage waveform W2 outputted fromthe oscillator 3 is compared with the voltage waveform W1 of the errorsignal. Here, when the voltage waveform W2 becomes higher than thevoltage waveform W1, the output of the PWM comparator 4 becomes H level.On the contrary, when the voltage waveform W2 becomes lower than thevoltage waveform W1, the output of the PWM comparator 4 becomes L level.For this reason, a waveform signal shown in FIG. 9(c) is outputted fromthe PWM comparator 4. This signal controls switching of the outputtransistor 6 through the drive transistor 5. In other words, when thePWM comparator 4 becomes H level, the output transistor 6 is turned off,and when L level, the output transistor 6 is turned on.

In the above switching operation, when the output transistor 6 is in ONstate, a current is supplied to the load 12 through the input terminalIN, the output transistor 6 and the coil 8. Moreover, when the outputtransistor 6 is in OFF state, the current, which is generated by energystored in the coil 8 while the output transistor 6 is in ON state, issupplied to the load 12 through the catch diode 7.

A current waveform which flows in the output transistor 6 is shown inFIG. 9(d), a current waveform which flows in the catch diode 7 is shownin FIG. 9(e) and a current waveform which flows in the coil 8 is shownin FIG. 9(f). At this time, a current, which is an average value W3 ofthe current flowing in the coil 8, is supplied to the load 12 as theoutput current.

As mentioned above, the regulator circuit 13 for controlling the pulsewidth of the voltage mode controls the output voltage V₀ based upon thedivided voltage of the voltage dividing circuit composed of theresistors 9 and 10 and the reference voltage of the reference voltagecircuit 1.

When a relationship D=t1/(t1+t2) holds where a period while the outputtransistor 6 is in ON state is t1, a period while in OFF state is t2,and ON-time/period of the output transistor 6 is duty D, the duty D isrepresented as follows:

    D=(V.sub.0 +V.sub.F)/V.sub.IN -V.sub.CE(sat) +V.sub.F.

Here,

V₀ : output voltage

V_(F) : forward voltage of the catch diode 7

V_(IN) : input voltage

V_(CE)(sat) : collector--emitter voltage of the output transistor 6

In other words, the periods t1 and t2 are determined by the outputvoltage V₀, the forward voltage V_(F) of the catch diode 7, the inputvoltage V_(IN), and the collector--emitter voltage V_(CE)(sat) of theoutput transistor 6.

FIG. 10 is a block diagram which shows an electrical configuration ofthe chopper-type regulator circuit for controlling the pulse width ofthe current mode. In the blocks of FIG. 10, the numerals of FIG. 8 aregiven to the blocks which have an arrangement similar to that of theblocks shown in FIG. 8.

A regulator circuit 16 is composed of the reference voltage circuit 1,the error amplifier 2, the oscillator 3, the PWM comparator 4, a flipflop 14, a current detection amplifier 15, a current detecting resistor17, the drive transistor 5 and the output transistor 6. In the regulatorcircuit 16, the pulse width of the current mode is controlled so thatthe output voltage is stabilized. Moreover, exterior components whichhas the arrangement same as of FIG. 8 are connected to the regulatorcircuit 16.

The following will explain an operation of the regulator circuit 16.FIGS. 11(a) through 11(h) are drawings which shows waveforms of mainsignals.

First, when the input voltage V_(IN) shown in FIG. 11(a) is applied tothe input terminal IN, the operation of the regulator circuit 16 isstarted up. The output voltage V₀ is divided by the voltage dividingcircuit composed of the resistors 9 and 10 connected to the load 12, thedivided voltage is fed back into the error amplifier 2 through afeedback terminal ADJ. Then, a voltage difference between the dividedvoltage and the reference voltage outputted from the reference voltagecircuit 1 is amplified by the error amplifier 2 and an error signal(differential voltage) is outputted. This error signal is represented bya voltage waveform W4 of FIG. 11(b).

The current flowing in the output transistor 6 is detected by thecurrent detecting resistor 17, and the current is converted into avoltage by the current detection amplifier 15, and the amplified voltageis outputted. Thereafter, a voltage waveform W5 showing the output ofthe current detection amplifier 15 and the voltage waveform W4 showingthe error signal are compared by the PWM comparator 4.

When the voltage outputted from the current detection amplifier 15becomes higher than the error voltage outputted from the error amplifier2, the output of the PWM comparator 4 becomes H level (see FIG. 11(c)),and the flip flop 14 is reset. The drive transistor 5 and the outputtransistor 6 are turned off by the reset. These OFF states continueuntil a pulse (see FIG. 11(d)) for setting the flip flop 14 is sent outfrom the oscillator 3. When the pulse is sent out, the OFF states areconverted into the ON states. FIG. 11(e) shows an output waveform of theflip flop 14.

In the above switching operation, when the output transistor 6 is in theON state, the current is supplied to the load 12 through the inputterminal IN, the output transistor 6 and the coil 8. Moreover, when theoutput transistor 6 is in the OFF state, the current, which is generatedby energy stored in the coil 8 while the output transistor 6 is in theON state, is supplied to the load 12 through the catch diode 7.

FIGS. 11(f), 11(g) and 11(h) are waveforms of main currents at the timeof control by the above-mentioned current mode: FIG. 11(f) is a currentwaveform flowing in the output transistor 6; FIG. 11(g) is a currentwaveform flowing in the catch diode 7; and FIG. 11(h) is a currentwaveform flowing in the coil 8. At this time, a current which is anaverage value W6 of the current flowing in the coil 8 is supplied as theoutput current to the load 12.

As mentioned above, the regulator circuit 16 for controlling the pulsewidth of the current mode supervises the current flowing in the currentdetecting resistor 17 so as to control the output voltage V₀ based uponthe divided voltage from the voltage dividing circuit composed of theresistors 9 and 10 and on the reference voltage from the referencevoltage circuit 1.

As to characteristics of these two kinds of the regulator circuits, theregulator circuit 13 for controlling the pulse width of the voltage modehas a simpler arrangement, but since the pulse width is changed afterthe output voltage V₀ is changed, the regulator circuit 13 has adisadvantage that follow-up to the change in the input voltage V_(IN) isdelayed.

Meanwhile, since the pulse width is changed accordingly to the change inthe input voltage V_(IN) before the output voltage V₀ is changed, theregulator circuit 16 for controlling the pulse width of the current modesatisfactorily follows up the change in the input voltage V_(IN) but itscircuit configuration is complex.

Besides the above two regulator circuits, there exists a chopper-typeregulator circuit for controlling pulse width of voltage mode whichutilizes a PNP-type transistor as the output transistor instead of anNPN-type transistor.

FIG. 12 is a block diagram which shows an electrical configuration ofthe above-mentioned chopper-type regulator circuit. The same numerals asin FIG. 8 are given to the blocks having an arrangement similar to thatof the blocks shown in FIG. 8 in the blocks of FIG. 12.

A regulator circuit 20 is composed of the reference voltage circuit 1,the error amplifier 2, the oscillator 3, the PWM comparator 4, an outputtransistor 18 which is a PNP-type transistor and a constant currentcircuit 21. Moreover, exterior components which have the samearrangement of FIG. 8 are connected to the regulator circuit 20.

The following will explain an operation of the regulator circuit 20.

First, when input voltage V_(IN) is applied to an input terminal IN, theregulator circuit 20 is actuated. Then, output voltage V₀ is divided bya voltage dividing circuit composed of resistors 9 and 10 connected to aload 12, and the divided voltage is fed back into a feedback terminalADJ. Since the feedback terminal ADJ is connected to a reverse input ofthe error amplifier 2, an error signal, which is generated by amplifyinga voltage difference between the divided voltage and a reference voltageoutputted from the reference voltage circuit 1, is outputted from theerror amplifier 2.

Meanwhile, a voltage outputted from the oscillator 3 is compared withthe error voltage outputted from the error amplifier 2 in the PWMcomparator 4, and a signal of H level or of L level is outputtedtherefrom. The constant current circuit 21 draws a base current of theoutput transistor 18 so as to actuate the output transistor 18.

When the output transistor 18 is in ON state, the input terminal IN, theoutput transistor 18 and the coil 8 are successively energized, and acurrent is supplied to the load 12. When the output transistor 18 is inOFF state, the current, which is generated by energy stored in the coil8 while the output transistor 18 is in ON state, is supplied to the load12 through the catch diode 7.

As to the above-mentioned three chopper-type regulator circuit, in achopper-type regulator circuit using an NPN-type transistor as an outputtransistor, an emitter-follower is adopted, so a voltage drop between acollector and an emitter in ON state becomes larger than that between acollector and an emitter of the PNP-type transistor. For this reason, aloss of the output transistor 6 is large, thereby raising a problem thatefficiency of a regulator circuit is lowered.

Meanwhile, as shown in FIG. 12, with the arrangement using the PNP-typetransistor as an output transistor, since a voltage drop between acollector and an emitter in ON state is small, a loss of the outputtransistor 18 is small. Therefore, efficiency of a regulator circuitbecomes high.

However, a PNP-type transistor as an output transistor hasdisadvantages. The disadvantages will be explained below.

When the output transistor 18 is in ON state, the constant currentcircuit 21 draws a base current of the output transistor 18. The basecurrent flows through the constant current circuit 21 into a groundterminal GND. The base current is normally constant irrespective of anoutput current, so it is dozens 10 mA. Moreover, since the regulatorcircuit 20 is generally used in a place where a voltage differencebetween an input voltage V_(IN) and an output voltage V₀ is large, ahigh input voltage V_(IN) is applied to the input terminal IN. For thisreason, when the regulator circuit using a PNP-type transistor iscompared the regulator circuits 13 and 16 using an NPN-type transistor,a drive loss represented by:

base current of output transistor 18×input voltage V_(IN) ×duty becomeslarge.

In addition, since the base current is constant in spite of a magnitudeof the load 12 when the output transistor 18 is in ON state, as shown bybroken lines B of FIG. 7 which is an explanatory drawing of the presentembodiment, the drive loss causes lowering of an efficiency especiallyat the time of a light load (low output current region).

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a chopper-typeregulator circuit, having an arrangement that uses a PNP-type transistoras an output transistor, which is capable of improving its efficiency bysupplying a base current of the output transistor, which flows intoground conventionally, directly to a load.

In order to achieve the above object, the chopper-type regulator circuitof the present invention includes an output transistor composed of aPNP-type transistor for switching an input current and a control sectionfor controlling the switching of the output transistor based upon avoltage difference between a reference voltage and an output voltage.Moreover, the chopper-type regulator circuit is characterized in thatthe control section includes a base current output terminal forsupplying a base current of the output transistor to a load connected tothe chopper-type regulator circuit.

With the above arrangement, since the base current output terminal foroutputting a base current flowing into the output transistor is providedto the control section, it is possible to take the base current outsidevia the output terminal. The base current output terminal is connectedto a load connected to the chopper-type regulator circuit, therebymaking it possible to directly supply the base current to the load. As aresult, the losses of the driving section can be reduced, therebyimproving efficiency.

In addition, it is a further object of the present invention to providea chopper-type regulator IC which makes it possible to miniaturize thechopper-types regulator circuit.

In order to achieve the above object, the chopper-type regulator IC ofthe present invention is characterized by including (1) a semiconductorchip obtained by integrating the output transistor and the controlsection into one chip, (2) a metal frame, which is mounted with thesemiconductor chip, having the base current output terminal and (3) apacking resin for sealing the semiconductor chip.

In addition, instead of the constitution (1), a semiconductor chip maybe obtained by integrating the output transistor and the control sectionrespectively into one chip.

With the above arrangement, since a chopper-type regulator IC can beobtained by providing a chopper-type regulator circuit as one package,it is possible to realize miniaturization of an IC.

In addition, in the case of the constitution (1), since a semiconductorchip is obtained by integrating an output transistor and a controlsection into one chip, it is possible to reduce a number of componentsand to lower its cost.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram which shows an electrical configuration of achopper-type regulator circuit for controlling a pulse width of avoltage mode of embodiment 1 of the present invention.

FIG. 2 is a circuit diagram which shows a concrete configuration of aconstant current circuit shown in FIG. 1.

FIG. 3 is a block diagram which shows an electrical configuration of achopper-type regulator circuit for controlling a pulse width of acurrent mode of embodiment 2 of the present invention.

FIG. 4 is a circuit diagram which shows a concrete configuration of aconstant current circuit shown in FIG. 3.

FIG. 5(a) is a plan view which shows an arrangement of a chopper-typeregulator IC of embodiment 3 of the present invention.

FIG. 5(b) is a side view of the above-mentioned chopper-type regulatorIC.

FIG. 6(a) is a plan view which shows an arrangement of anotherchopper-type regulator IC.

FIG. 6(b) is a side view of the above-mentioned chopper-type regulatorIC.

FIG. 7 is a graph which shows a relationship between an output currentand efficiency in a chopper-type regulator circuit.

FIG. 8 is a block diagram which shows an electrical configuration of aconventional chopper-type regulator circuit for controlling a pulsewidth of a voltage mode.

FIGS. 9(a) through 9(f) are waveform diagrams which shows waveforms ofmain signals of the chopper-type regulator circuit shown in FIG. 8.

FIG. 10 is a block diagram which shows an electrical configuration of aconventional chopper-type regulator circuit for controlling a pulsewidth of a current mode.

FIGS. 11(a) through 11(h) are waveform diagrams of main signals of thechopper-type regulator circuit shown in FIG. 10.

FIG. 12 is a block diagram which shows an electrical configuration ofanother conventional chopper-type regulator circuit for controlling apulse width of a voltage mode.

DESCRIPTION OF THE EMBODIMENTS EMBODIMENT 1!

The following describes embodiment 1 of the present invention withreference to FIG. 2 and FIG. 7.

FIG. 1 is a block diagram which shows an electrical configuration of achopper-type regulator circuit for controlling a pulse width of avoltage mode (i.e. a regulator circuit). The same reference numerals ofFIG. 12 are given to blocks of FIG. 1 which have the same configurationas the blocks shown in FIG. 12.

A regulator circuit 31 is composed of a reference voltage circuit 1, anerror amplifier 2 (voltage difference output means), an oscillator 3, aPWM (Pulse Width Modulation) comparator 4 (comparing means), an outputtransistor 18 which is a PNP-type transistor and a constant currentcircuit 19 (constant current means). The regulator circuit 31 controls apulse width of a voltage mode so as to stabilize an output voltage.

In addition, a catch diode 7, a coil 8, a voltage dividing circuitcomposed of two resistors 9 and 10 and an output capacitor 11 which areindispensable elements are externally mounted to the regulator circuit31. But for them, an output voltage cannot be obtained (12 of FIG. 1represents a load). Circuit components other than the output transistor18 are control sections.

The reference voltage circuit 1 generates a reference voltage wherein achange in response to an input voltage V_(IN) applied to an inputterminal IN and a change with temperature are extremely small. In otherwords, the reference voltage is a stabilized prescribed voltage. Thegenerated reference voltage is sent to an non-reverse input of the erroramplifier 2.

The error amplifier 2 amplifies a voltage difference between a voltage(divided voltage) led to a feedback terminal ADJ connected to a reverseinput and the reference voltage so as to output the voltage as an errorsignal. The error signal is sent to a non-reverse input of the PWMcomparator 4.

The oscillator 3 composed of an integrating circuit, etc. for a constantcurrent generates an a.c. wave. The generated a.c. wave is sent to areverse input of the PWM comparator 4.

The PWM comparator 4 compares an a.c. wave generated by the oscillator 3with an error signal.

In order to lower a voltage between a collector and an emitter which arein ON state so as to reduce a loss of the collector, a PNP-typetransistor is used as the output transistor 18. A current led to theinput terminal IN is switched, and the switched current is sent to anoutput terminal.

When the output transistor 18 is turned ON based upon an output of thePWM comparator 4, the constant current circuit 19 draws a base currentof the output transistor 18 and controls such that the base currentbecomes constant whether an input voltage V_(IN) is high or low.Moreover, the base current is led to a base current output terminal IB.

When the output transistor 18 is turned OFF, the catch diode 7 wherein acathode is connected to the output terminal OUT and anode is groundedforms a closed circuit between the coil 8 and a load 12. A currentgenerated by energy stored in the coil 8 flows to the catch diode 7.

The coil 8 stores and releases energy when the output transistor 18 isswitched. Since the catch diode 7 and the output capacitor 11 arepaired, the coil 8 converts a switched voltage into a d.c. voltage.

The voltage divided circuit composed of the two resistors 9 and 10 setsa voltage applied to the load 12. Moreover, the voltage divided circuitgenerates a divided voltage to be sent to the feedback terminal ADJ.

The base current output terminal IB is directly connected to the load12, and the base current output terminal IB supplies the base currentdrawn by the constant current circuit 19 to the load 12.

In FIG. 1, the regulator circuit 31 is sealed in a package of achopper-type regulator IC. The sealing arrangement is mentioned later.

The following describes an operation of the regulator circuit 31.

First, when an input voltage V_(IN) is applied to the input terminal IN,the regulator circuit 31 is actuated. Then, an output voltage V₀ isdivided by the voltage dividing circuit composed of the resistors 9 and10 connected to the load 12, and the divided voltage is fed back to thefeedback terminal ADJ. Since the feedback terminal ADJ is connected tothe reverse input of the error amplifier 2, an error signal(differential voltage), which is obtained by amplifying a voltagedifference between the divided voltage and a reference voltage outputtedfrom the reference voltage circuit 1, is outputted from the erroramplifier 2.

Meanwhile, in the PWM comparator 4, a voltage outputted from theoscillator 3 is compared with the error voltage outputted from the erroramplifier 2. When the voltage from the oscillator 3 is higher than theerror voltage, the PWM comparator 4 outputs a control signal with Hlevel, and when the voltage from the oscillator 3 is lower than theerror voltage, the PWM comparator 4 outputs a control signal with Llevel. The constant current circuit 19 draws a base current of theoutput transistor 18 based upon the control signal, and the outputtransistor 18 is actuated (switched). In other words, when the controlsignal is at H level, the output transistor 18 is turned OFF, and whenthe control signal is at L level, the output transistor 18 is turned ON.

When the output transistor 18 is in ON state (an output of the PWMcomparator 4 is at L level), a current successively flows to the inputterminal IN, the output transistor 18 and the coil 8, and the current issupplied to the load 12. Further, the base current of the output:transistor 18 flows to the base current output terminal IB via theconstant current circuit 19 so as to be supplied to the load 12.

When the output transistor 18 is in OFF state (an output of the PWMcomparator 4 is at H level), a current, which is generated by energystored in the coil 8 while the output transistor 18 is in ON state, issupplied to the load 12 via the catch diode 7.

The following concretely describes a configuration of the constantcurrent circuit 19 of the present embodiment and its operation.

FIG. 2 is a drawing which explains a configuration of the constantcurrent circuit 19 in FIG. 1. A constant current circuit 19 is composedof PNP-type transistors 61 and 62 (fourth and fifth transistors),NPN-type transistors 63, 64 and 65 (third, second and firsttransistors), a resistor 67 and a voltage source 66 (reference currentgenerating means). The voltage source 66 is a voltage source created ina regulator (for example, band gap reference).

The NPN-type transistor 64 and the resistor 67 are connected in parallelto the voltage source 66. Moreover, a base of the NPN-type transistor 64is connected to a base of the NPN-type transistor 63. Namely, since theNPN-type transistors 63 and 64 are arranged so as to have a currentmirror structure, a current I₁, which is obtained by the ratio of areasof emitters in the NPN-type transistors 63 and 64, flows to the NPN-typetransistor 63, and the same current I₁ flows also to the PNP-typetransistor 61.

A collector of the NPN-type transistor 65 is connected between bases ofthe NPN-type transistors 63 and 64, and a base of the NPN-typetransistor 65 is connected to an output of the PWM comparator 4. Theemitters of NPN-type transistors 63, 64 and 65 are grounded.

In addition, the PNP-type transistor 61 is connected between the base ofthe output transistor 18 and the collecter of the NPN-type transistor63. A base of the PNP-type transistor 61 is connected to a base of thePNP-type transistor 62. Since the PNP-type transistors 61 and 62 arearranged so as to have a current mirror structure, a current (basecurrent I_(B)), which is obtained by the ratio of areas of emitters inthe PNP-type transistors 61 and 62, flows to the PNP-type transistor 62.

When the area of the emitter in the PNP-type transistor 62 to the areaof the emitter in the PNP-type transistor 61 is sufficiently enlarged, aloss of the constant current circuit 19 can be reduced. As to the ratioof the areas of the emitters, for example, PNP-type transistor61:PNP-type transistor 62=1:50.

The resistor 67 and the voltage source 66 are necessary for generating areference current I which keeps the base current. I_(B) of the outputtransistor 18 constant. The reference current I is represented asfollows:

I=(V₀ -V_(BE))/R

wherein:

V₀ =a voltage of the voltage source 66;

V_(BE) =a voltage between the base and emitter in the NPN-typetransistor 64; and

R=resistance of the resistor 67.

Therefore, according to a current mirror of the NPN-type transistors 63and 64, the current I₁ is represented as follows:

I₁ =(area of emitter in Transistor 63/area of emitter in Transistor64)×I.

Moreover, according to a current mirror of the PNP-type transistors 61and 62, the base current I_(B) of the output transistor 18 isrepresented as follows:

I_(B) =(area of emitter in Transistor 62/area of emitter in Transistor61)×I₁.

Therefore, the base current I_(B) becomes steady current.

The following describes an operation of a circuit having the aboveconfiguration. An NPN-type transistor 65 is turned ON/OFF based upon acontrol signal outputted from the PWM comparator 4, and the outputtransistor 18 is turned ON/OFF. Usually, when the NPN-type transistor 65is turned OFF, the output transistor 18 is turned ON. In other words,when an output of the PWM comparator 4 is at L level, the NPN-typetransistor 65 is turned OFF, and the NPN-type transistor 64 isenergized. Therefore, when the output transistor 18 is turned ON, thebase current I_(B) of the output transistor 18 flows to the base currentoutput terminal IB through the PNP-type transistor 62 and reaches theload 12.

In such a manner, the constant current circuit 19 is capable of drivinga base current I_(B) of the output transistor 18 at constant currentwhether an input voltage V_(IN) is high or low. Moreover, an excessiveloss of the base current I_(B) can be prevented.

For example, when an input voltage V_(IN) is 24V, an output voltage V₀is 12V and a base current I_(B) of the output transistor 18 is 50 mA, aloss M₁ of the regulator circuit 31 is represented as follows: ##EQU1##wherein:

D=(V₀ +V_(F))/(V_(IN) -V_(CE)(sat) +V_(F)),

V_(F) : forward voltage of catch diode 7 ≅0.5 V

V_(CE)(sat) : voltage drop between collector and emitter in outputtransistor 18 ≅0.5 V

Ic: collector current of output transistor 18

I_(Q) : current consumption.

In addition, for comparison, a loss M₂ of a conventional regulatorcircuit 20 shown in FIG. 12 is represented as follows: ##EQU2##

Therefore, when the regulator circuit 31 of the present embodiment iscompared with the conventional regulator circuit 20 in FIG. 12, lossesof their output transistors 18 and losses of the control sections aresame, but losses of base currents I_(B) of the output transistors 18 canbe reduced 0.312 (W) (=0.624 (W) -0.312(W)). Moreover, since a PNP-typetransistor is used as the output transistor 18 in the regulator circuit31, a voltage drop between the collector and the emitter can be reduced.

Therefore, since the regulator circuit 31 of the present embodiment canreduce the loss of the regulator circuit 31, efficiency of a circuit isimproved as shown by a solid line A of FIG. 7. FIG. 7 shows efficiencyof the conventional regulator circuit 31 (solid line A) and of theregulator circuit 20 (broken line B) when an input voltage V_(IN) is24V, an output voltage V₀ is 12V, a base current I_(B) of the outputtransistor 18 is 50 mA and current consumption I_(Q) is 20 mA.

EMBODIMENT 2!

The following will describe embodiment 2 of the present invention withreference to FIG. 3 and FIG. 4. Here, for convenience of explanation,those members that have the same arrangement and functions, and that aredescribed in the aforementioned embodiment 1 are indicated by the samereference numerals and the description thereof is omitted.

FIG. 3 is a block diagram which shows an electrical configuration of achopper-type regulator circuit for controlling a pulse width of acurrent mode. A regulator circuit 32 is composed of a reference voltagecircuit 1, an error amplifier 2, an oscillator 3, a PWM comparator 4, aPNP-type output transistor 18, a flip flop 14, a current detectionamplifier 15, a current detecting resistor 17 and a constant currentcircuit 19. Moreover, external components having the same arrangementsas in FIG. 1 are connected to the regulator circuit 32. Circuit partsother than the output transistor 18 constitute a control section.

The following describes an operation of the regulator circuit 32.

First, when an input voltage V_(IN) is applied to an input terminal IN,the regulator circuit 32 is actuated. Then, an output voltage V₀ isdivided by a voltage dividing circuit composed of resistors 9 and 10connected to a load 12, and the divided voltage is fed back to afeedback terminal ADJ. Since the feedback terminal ADJ is connected to areverse input of the error amplifier 2, a voltage difference between thedivided voltage and a reference voltage outputted from the referencevoltage circuit 1 is amplified so that an error signal (differentialvoltage) is outputted from the error amplifier 2.

Meanwhile, in the PWM comparator 4, a current which flows to the outputtransistor 18 is detected as a voltage by the current detecting resistor17, a voltage, which is amplified by the current detection amplifier 15,is compared with the differential voltage outputted from the erroramplifier 2. Then, a set signal (first set signal) is outputted from thePWM comparator 4.

When the voltage of the current detection amplifier 15 becomes higherthan the differential voltage outputted from the error amplifier 2, anoutput of the PWM comparator 4 is at H level, and the flip flop 14 isreset. Then, the output transistor 18 is turned OFF, and the outputtransistor 18 is kept in OFF state until a set signal (second setsignal) is inputted from the oscillator 3 to the flip flop 14. When theset signal is inputted to the flip flop 14, the constant current circuit19 draws the base current of the output transistor 18 so that the outputtransistor 18 is actuated.

In other words, when the output transistor 18 is in ON state, currentsuccessively flows to the input terminal IN, the output transistor 18and the coil 8 and is supplied to the load 12. Furthermore, base currentof the output transistor 18 flows to the base current output terminal 1Bthrough the constant current circuit 19 so as to be supplied to the load12. Meanwhile, when the output transistor 18 is in OFF state, a current,which is generated by energy stored in the coil 8 while the outputtransistor 18 is in ON state, is supplied to the load 12 through thecatch diode 7.

Next, FIG. 4 shows a connecting state of a constant current circuit 19in the present embodiment that is same as the circuit described inaforementioned embodiment 1. Only different points from embodiment 1 inoperation of the constant current circuit 19 are described.

The constant current circuit 19 turns ON/OFF an NPN-type transistor 65based upon an output signal of the flip flop 14 and then turns ON/OFFthe output transistor 18. In other words, when an output of the flipflop 14 becomes L level, the NPN-type transistor 65 is turned OFF, andthe output transistor 18 is turned ON. Moreover, when an output of theflip flop 14 becomes H level, the NPN-type transistor 65 is turned ON,and the output transistor 18 is turned OFF.

In the same manner as of the regulator circuit 31 of embodiment 1 forcontrolling a pulse width of a voltage mode, in the regulator circuit 32for controlling a pulse width of a current mode, since a base current ofthe output transistor 18 is supplied to the load 12 through the basecurrent output terminal IB, a loss of a base current can be reduced fora value of the product of output voltage (V₀), base current (I_(B)) ofoutput transistor 18 and duty (D), which is represented by the equation(1). In addition, a loss of output transistor 18 can be reduced bydecreasing a voltage drop between a collector and an emitter using aPNP-type output transistor 18. As a result, efficiency of the regulatorcircuit 32 can be improved.

A chopper-type regulator circuit of the present invention forstabilizing an output voltage includes a PNP-type output transistor anda control section for control switching of the output transistor basedupon a voltage difference between a reference voltage and an outputvoltage. A base current output terminal, which is connected to a base ofan output transistor and which outputs a base current flowing into theoutput transistor, is provided to the control section.

With respect to the above arrangement, since the base current outputterminal for outputting a base current flowing into the outputtransistor is connected to the base of the output transistor, it ispossible to take out a base current, which flows into the outputtransistor, to the outside. When the base current output terminal and aload connected to the chopper-type regulator circuit are connected, thebase current of the output transistor can be directly supplied to theload. This makes it possible to reduce a loss of a driving section,thereby improving efficiency.

In addition, the chopper-type regulator circuit can be arranged so as toinclude a constant current circuit between the base of the outputtransistor and the base current output terminal.

As a result, when the output transistor is turned ON, the constantcurrent circuit draws a base current of the output transistor so thatthe base current can be kept constant whether an input voltage is highor low. Consequently, an excessive loss of a base current of the outputtransistor can be prevented.

EMBODIMENT 3!

The following describes embodiment 3 of the present invention withreference to FIG. 5 and FIG. 6. Here, for convenience of explanation,those members that have the same arrangement and functions, and that aredescribed in the aforementioned embodiments are indicated by the samereference numerals and the description thereof is omitted.

A chopper-type regulator circuit having a circuit configurationdescribed in aforementioned embodiments 1 and 2 is integrated as achopper-type regulator IC by an inner configuration mentioned below, forexample.

As shown in FIGS. 5(a) and 5(b), a chopper-type regulator IC 39aincludes a semiconductor chip 40 obtained by integrating a transistorsection 41 and a control section 42 into one chip. The transistorsection 41 is composed of an output transistor 18, and the controlsection 42 is obtained by integrating the above-mentioned components andcircuits other than the output transistor 18.

The semiconductor chip 40 is stuck to a metal frame 44 by die-bonding ajoining section 43 composed of solder.

One end of the metal frame 44 is extended so that an outer lead frame 45is formed, and this section is a ground terminal GND. Moreover, an outerlead frame 46 which is an input terminal IN, an outer lead frame 47which is an output terminal OUT, an outer lead frame 48 which is a basecurrent output terminal IB and an outer lead frame 49 which is afeedback terminal ADJ are provided on the right side of the outer leadframe 45 viewed looking at FIG. 5(a) so as to be parallel with the outerlead frame 45.

In the transistor section 41, a contact section 41a which is an emitteris connected to the outer lead frame 46, and a contact section 41b whichis a collector is connected to the outer lead frame 47.

In the control section 42, a contact section 42a for a base is connectedto the outer lead frame 48, a contact section 42c for grounding isconnected to the metal frame 44 and a contact section 42b for feedbackis connected to the outer lead frame 49.

The above connections are wire-bonded by metal wire 50. Moreover, thetransistor section 41, the control section 42, the metal frame 44 andalso one ends of the outer lead frames 45 through 49 are coated with apackage 51. The package 51 is composed of packing resin, such as epoxyresin, and it is formed by a transfer molding method or the like.

In the chopper-type regulator IC 39a, the regulator circuits 31 and 32can be incorporated as one package, thereby realizing miniaturization.Moreover, the transistor section 41, which is composed of the outputtransistor 18, and the control section 42 are integrated as thesemiconductor chip 40, thereby making it possible to reduce a number ofcomponents and to lower cost.

The following describes another arrangement example of the chopper-typeregulator IC 39a.

As shown in FIGS. 6(a) and 6(b), a chopper-type regulator IC 39b has twochips; a transistor chip 52 and an IC chip 53. The transistor chip 52 iscomposed of an output transistor 18 as one chip, and the IC chip 53 isobtained by integrating the above elements and circuits other than theoutput transistor 18 into one chip.

The transistor chip 52 is stuck to a metal frame 44 by die-bonding ajoining section 43 composed of solder. The IC chip 53 is stuck to themetal frame 44 by die-bonding insulating paste 54.

One end of the metal frame 44 is extended so that an outer lead frame 55is formed thereon, and this section is an output terminal OUT. Moreover,an outer lead frame 56 which is an input terminal IN, an outer leadframe 57 which is a base current output terminal IB, an outer lead frame58 which is a ground terminal GND and an outer lead frame 59 which is afeedback terminal ADJ are provided to the right side of the outer leadframe 55 viewed looking at FIG. 6(a) so as to be parallel with the outerlead frame 55.

As to the transistor chip 52, a contact section 52a which is an emitteris connected to the outer lead frame 56, a contact section 52b which isa base is connected to a contact section 53d for a control circuit ofthe IC chip 53, and a collector electrode is stuck to the outer leadframe 55 by solder 43 so as to be connected thereto.

As to the IC chip 53, a contact section 53e for input is connected tothe outer lead frame 56, a contact section 53b for grounding isconnected to the outer lead frame 58, a contact section 53a for a basecurrent is connected to the outer lead frame 57, and a contact section53c for feedback is connected to the outer lead frame 59.

The above connections are wire-bonded by a metal wire 50. Moreover, thechips 52 and 53, the metal frame 44 and one ends of the outer leadframes 55 through 59 are coated with a package 51. The package 51 iscomposed of packing resin, such as epoxy resin, and it is formed by thetransfer molding method or the like.

In the same manner as of the chopper-type regulator IC 39a, in thechopper-type regulator IC 39b, the regulator circuits 31 and 32 can beincorporated into one package, thereby realizing miniaturization.

The chopper-type regulator IC of the present invention is characterizedby including (1) a semiconductor chip obtained by integrating the outputtransistor and the control section into one chip or a semiconductor chipcomposed of each chip of the output transistor and of the controlsection, (2) a metal frame composed of the semiconductor chip and thebase current output terminal and (3) packing resin for sealing thesemiconductor chip.

As a result, a chopper-type regulator circuit can be arranged as onepackage, thereby realizing miniaturization.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A chopper-type regulator circuit for stabilizing an output voltage, comprising:a single-structure output transistor composed of a PNP-type transistor for switching an input current to a first output terminal; and a control section for controlling the switching of said output transistor between ON and OFF states based upon a voltage difference between a reference voltage and the output voltage, such that said control section controls a duty ratio of the output voltage, wherein said control section includes a base current output terminal for supplying a base current of said output transistor to a load connected to said chopper-type regulator circuit, the base current being supplied to the load whenever said output transistor is in an ON state.
 2. The chopper-type regulator circuit as defined in claim 1, wherein said output transistor includes a collector, said collector being connected directly to said first output terminal.
 3. The chopper-type regulator circuit as defined in claim 1, further comprising:a metal frame mounted with said regulator circuit, said first output terminal and said base current output terminal extending from said metal frame; and a packing resin for sealing said regulator circuit.
 4. The chopper-type regulator circuit as defined in claim 1, wherein said control section controls a pulse width of a voltage mode.
 5. The chopper-type regulator circuit as defined in claim 4, wherein said control section includes:a voltage difference output means for outputting a voltage difference between the reference voltage and the output voltage; a comparison means for comparing the output signal from said voltage difference output means with a prescribed pulse signal so as to output a control signal; and a constant current means for drawing the base current so as to keep a value of the base current constant when said output transistor is in conducting state based upon the control signal, said constant current means being connected between a base of said output transistor and said base current output terminal.
 6. The chopper-type regulator circuit as defined in claim 1, wherein said control section controls a pulse width of a current mode.
 7. The chopper-type regulator circuit as defined in claim 6, wherein said control section includes:a voltage difference output means for outputting a voltage difference between the reference voltage and the output voltage; a comparison means for comparing an output from said voltage difference output means with a current flow in said output transistor so as to output a first set signal; a flip flop for switching said output transistor based upon the first set signal and a prescribed second set signal; and a constant current means for drawing the base current so as to keep a value of the base current constant when said output transistor is brought to a conducting state by said switching operation via said flip flop, said constant current means being connected between a base of said output transistor and said base current output terminal.
 8. The chopper-type regulator circuit as defined in claim 1, wherein said control section includes a first transistor having a collector and an emitter, said emitter being connected to a base of said output transistor, and said collector being connected directly to said base current output terminal.
 9. The chopper-type regulator circuit as defined in claim 8, wherein said control section further includes a second transistor having a base connected to a base of said first transistor, said second transistor having an emitter connected to the base of the output transistor.
 10. The chopper-type regulator circuit as defined in claim 1, further comprising a circuit element connected between said first output terminal and said base current output terminal.
 11. The chopper-type regulator circuit as defined in claim 10, wherein said circuit element is a coil.
 12. The chopper-type regulator circuit as defined in claim 1, wherein said output transistor and said control section are integrated into a single semiconductor chip.
 13. The chopper-type regulator circuit as defined in claim 12, further comprising a metal frame mounted with said semiconductor chip, said first output terminal and said base current output terminal extending from said metal frame.
 14. The chopper-type regulator circuit as defined in claim 12, further comprising a packing resin for sealing said semiconductor chip. 